Formic acid as an alternative reducing agent for the catalytic nitrate reduction in aqueous media

• Published in: Journal of environmental sciences (China) 2013-08, Vol.25 (8), p.1696-1702
• Main Authors: Choi, Eun-kyoung, Park, Kuy-hyun, Lee, Ho-bin, Cho, Misun, Ahn, Samyoung
• Format: Article
• Language: English
• Subjects: ammonia; bicarbonates; Catalysis; catalysts; catalytic nitrate reduction; Formates - chemistry; formic acid; H2 supply; hydrogen; metals; Microscopy, Electron, Scanning; Microscopy, Electron, Transmission; nitrate reduction; nitrates; Nitrates - chemistry; nitrites; Oxidation-Reduction; particles; Pd:Cu/λ-alumina catalyst; reducing agents; scanning electron microscopy; Solutions; Water - chemistry; 亚硝酸盐; 双金属催化剂; 含水介质; 氧化铝催化剂; 甲酸; 表面特性; 还原剂; 透射电子显微镜
• ISSN: 1001-0742; 1878-7320
• DOI: 10.1016/S1001-0742(12)60226-5

Formic acid was used for the nitrate reduction as a reductant in the presence of Pd：Cu/γ-alumina catalysts. The surface characteristics of the bimetallic catalyst synthesized by wet impregnation were investigated by SEM, TEM-EDS. The metals were not distributed homogeneously on the surface of catalyst, although the total contents of both metals in particles agreed well with the theoretical values. Formic acid decomposition on the catalyst surface, its influence on solution pH and nitrate removal efficacy was investigated. The best removal of nitrate （50 ppm） was obtained under the condition of 0.75 g/L catalyst with Pd：Cu ratio （4：1） and two fold excess of formic acid. Formic acid decay patterns resembled those of nitrate removal, showing a linear relationship between kf （formic acid decay） and k （nitrate removal）. Negligible amount of ammonia was detected, and no nitrite was detected, possibly due to buffering effect of bicarbonate that is in situ produced by the decomposition of formic acid, and due to the sustained release of H2 gas.